1. Field of the Invention
This invention relates to electronically controlled on/off cycling of pumps and such in which the ability to set the cycle over wide ranges for on-time, off-time, and total time of one cycle is desirable.
2. Description of the Related Art including information disclosed under 37 C.F.R. Sections 1.97-1.99
Fishermen often carry various kinds of live bait which are kept alive in a "livewell," filled with fresh or salt water, as appropriate. In order to keep the bait alive and fresh, the water in the livewell must be refreshed. If the livewell is in a boat, this is sometimes done by pumping in water from outside the boat into the livewell, and expelling the old water. Another technique is to use an aerator to maintain proper gas balance within the livewell.
Most frequently, the livewell pump is simply left on constantly, and the only form of control is for the operator to turn it on and off manually. Leaving the pump on continuously rapidly drains the battery that runs the pump. This is a particularly serious problem for offshore marine fishermen, who may use an engine-starting storage battery for this purpose. This means the operator must use care not to discharge the battery to the point where the engine cannot be restarted, or else must idle the engine to keep the battery charged. Idling the engine not only consumes gasoline, but also may disturb the fishing in the area of the boat.
Fishermen have also discovered that various kinds of live bait require different levels of water quality in the livewell. Menhaden, for instance, are very sensitive to poor water quality and require frequent replenishment, whereas live shrimp are quite hardy, and will survive well with infrequent aeration and/or replenishment of the water in the livewell.
For these two reasons, an automatic control system that will control the pump that maintains water quality in the livewell is needed. It should allow for just enough pump operation to maintain water quality for the specific live bait in the livewell, but no more. In so doing, it will make most efficient use of the battery.
There are such control devices on the market, but they have serious limitations. One such device has a fixed cycle time of 15 minutes, and the operator may set the on-time up to 71/2 minutes. The remainder of the 15 minute cycle constitutes the off-time. While this will work for some situations, it would not allow (for instance) for 2 minutes on, 28 minutes off, which would be adequate for some situations, depending on pumping speed, the livewell capacity, and type of live bait.
A second such device offers a fixed on-time of 30 seconds, whereas the off-time is adjustable from 90 seconds to 5 minutes. Again, this is too limited a range of control. For many applications, each time the pump is on, a complete change of the livewell water is desirable. Depending on the livewell capacity and the pumping speed, 30 seconds may be completely inadequate to provide for one complete change.
The devices of which we are aware limit themselves to resistive/capacitive elements to provide the timing function. Since long time delays are sometimes desired, the large capacity capacitors needed are both expensive, and (when electrolytics) are subject to current leakage and breakdown, particularly in the high stress environment of a boat.
Our device uses a frequency divider with a feedback switching circuit, and we believe our usage is a unique improvement over the prior art. U.S. Pat. No. 4,958,228 to Kutsuki (1990) for an Automatic Frequency Change Device, does have two oscillators, the output of one of which is switched to the input of a frequency divider. But the switch is not really a feedback switch which enables operation in an astable mode, but rather the circuit samples an input signal to set the switch one way or the other. Another difference is, of course, the application; the Automatic Frequency Change Device applies to the sensing and gating of different types of video signals.
U.S. Pat. No. 3,938,009 to Gauthier (1974) for Precision Control of Relay Operate and Release Timer is for a different application, which is to control very short time delays in the operating and/or releasing of a relay, based on a fixed frequency clock, and an input control signal for the switching of the relay. Our invention is in contrast an astable, cycling control, rather than one that depends on an external signal to operate or release the relay. In addition, in our device the clock signals are adjustable in frequency.
Frequency divider integrated circuits are rated on how high a frequency they can handle. We believe one unique use of the frequency divider in our system is its use at low, audio level frequencies. Our interest is not in how fast a signal it can handle, but in its ability to count large numbers of cycles before the output changes state. A relatively high frequency controlled signal, which uses a small capacitor for timing, can be fed into the frequency divider, and the larger the number of cycles it counts, the longer it will delay before its output changes state. This long delay is thus accomplished by a small, reliable, compact integrated circuit, rather than a large capacitor.